A new, compact, high voltage vacuum interrupter has been developed. This interrupter has been incorporated into a cost effective, retrofit kit to upgrade 121 kV-145 kV, oil circuit breakers from 10 kA and 20 kA to 40 kA. Extensive testing of a breaker retrofitted with this kit shows that it will satisfy the existing ANSI standards. The retrofit kit not only considerably extends the breaker's life, but it also provides a significant reduction of breaker naintenance.